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12/10/14, 1:ML Tutorial

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UML Tutorial

UML is a standard language for specifying, visualizing, constructing, and

documenting the artifacts of software systems.

UML was created by Object Management Group and UML 1.0 specification

draft was proposed to the OMG in January 1997.

This tutorial gives a complete understanding on UML.

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Quick Links for UML Engineers

(1) UML Quick Reference Guide

A quick UML reference guide for UML Engineers.

UML Quick Reference Guide

(2) Useful UML Resources

A collection ofUML

Sites, Books and Articles is given at this page.

Useful UML Resources

(3) UML Tools and Utilities

Here you will find a useful UML's tools and utilities which you will require very frequently while doing

UML modeling.

UML Tools and Utilities

(4) UML Knowledge Test

Measure your knowledge by going through simple but tricky UML questions from the whole tutorial.

Test Your Knowledge

(5) UML Tutorial in PDF

Download a quick Servlets tutorial in UML format.

UML Tutorial in PDF

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12/10/14, 1:ML - Quick Guide (Summary)

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UML Quick Guide ( Summary )

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UML Overview:

UML is a general purpose modeling language. It was initially started to capture the behavior of complex

software and non software system and now it has become an OMG standard.

UML provides elements and components to support the requirement of complex systems. UML follows

the object oriented concepts and methodology. So object oriented systems are generally modeled usin

the pictorial language.

UML diagrams are drawn from different perspectives like design, implementation, deployment etc.

At the conclusion UML can be defined as a modeling language to capture the architectural, behavioral

and structural aspects of a system.

Objects are the key to this object oriented world. The basic requirement of object oriented analysis and

design is to identify the object efficiently. After that the responsibilities are assigned to the objects.

Once this task is complete the design is done using the input from analysis.

The UML has an important role in this OO analysis and design, The UML diagrams are used to model th

design. So the UML has an important role to play.

UML notations:

UML notations are the most important elements in modeling. Efficient and appropriate use of notations

is very important for making a complete and meaningful model. The model is useless unless its purpos

is depicted properly.

So learning notations should be emphasized from the very beginning. Different notations are available

for things and relationships. And the UML diagrams are made using the notations of things and

relationships. Extensibility is another important feature which makes UML more powerful and flexible.

UML Diagrams:

Diagrams are the heart of UML. These diagrams are broadly categorized as structural and behavioral

diagrams.

Structural diagrams are consists of static diagrams like class diagram, object diagram etc.

Behavioral diagrams are consists of dynamic diagrams like sequence diagram, collaboration

diagram etc.

The static and dynamic nature of a system is visualized by using these diagrams.

Class diagrams:

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Class diagrams are the most popular UML diagrams used by the object oriented community. It

describes the objects in a system and their relationships. Class diagram consists of attributes and

functions.

A single class diagram describes a specific aspect of the system and the collection of class diagrams

represents the whole system. Basically the class diagram represents the static view of a system.

Class diagrams are the only UML diagrams which can be mapped directly with object oriented

languages. So it is widely used by the developer community.

Object Diagram:

An object diagram is an instance of a class diagram. So the basic elements are similar to a class

diagram. Object diagrams are consists of objects and links. It captures the instance of the system at a

particular moment.

Object diagrams are used for prototyping, reverse engineering and modeling practical scenarios.

Component Diagram:

Component diagrams are special kind of UML diagram to describe static implementation view of a

system. Component diagrams consist of physical components like libraries, files, folders etc.

This diagram is used from implementation perspective. More than one component diagrams are used to

represent the entire system. Forward and reverse engineering techniques are used to make executable

from component diagrams.

Deployment Diagram:

Component diagrams are used to describe the static deployment view of a system. These diagrams are

mainly used by system engineers.

Deployment diagrams are consists of nodes and their relationships. An efficient deployment diagram is

an integral part of software application development.

Use Case Diagram;

Use case diagram is used to capture the dynamic nature of a system. It consists of use cases, actors

and their relationships. Use case diagram is used at a high level design to capture the requirements of

a system.

So it represents the system functionalities and their flow. Although the use case diagrams are not a

good candidate for forward and reverse engineering but still they are used in a slightly differently way

to model it.

Interaction Diagram:

Interaction diagrams are used for capturing dynamic nature of a system. Sequence and collaboration

diagrams are the interaction diagrams used for this purpose.

Sequence diagrams are used to capture time ordering of message flow and collaboration diagrams are

used to understand the structural organization of the system. Generally a set of sequence and

collaboration diagrams are used to model an entire system.

Statechart Diagram:





Statechart diagrams are one of the five diagrams used for modeling dynamic nature of a system. These

diagrams are used to model the entire life cycle of an object. Activity diagram is a special kind of

Statechart diagram.

State of an object is defined as the condition where an object resides for a particular time and the

object again moves to other states when some events occur. Statechart diagrams are also used for

forward and reverse engineering.

Activity Diagram:Activity diagram is another important diagram to describe dynamic behaviour. Activity diagram consist

of activities, links, relationships etc. It models all types of flows like parallel, single, concurrent etc.

Activity diagram describes the flow control from one activity to another without any messages. These

diagrams are used to model high level view of business requirements.






12/10/14, 1:ML - Useful Resources

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UML Useful Resources

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[email protected]

Object Management Group - OMG Unified Modeling Language Specification.

UML @ Wiki - Good tutorial on UML.

UML® Resource Page - A listing of various other resources for UML.

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http://www.uml.org/

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12/10/14, 1:ML - Tools & Utilities

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UML Tools & Utilities

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If you want to list down your website, book or any other resource on this page then please contact at

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StarUML - StarUML is an open source project to develop fast, flexible, extensible, featureful, and

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http://www.genmymodel.com/

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http://argouml.tigris.org/

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12/10/14, 1:ML - Knowledge Test

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UML Knowledge Test

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This chapter list down simple questions on UML concepts you just have gone through this tutorial.

Based on the given set of questions you can assess yourself to build a good confidence to become an

UML expert:

Can a class diagram show the dynamic behaviour of a system?

Can deployment diagram be used for forward and reverse engineering?

Can it be used for forward and reverse engineering?

Can it represent parallel flow of activities?

Can we convert statechart diagram to activity diagram?

Can we use forward engineering in component diagram?

Can we use the use case diagram for forward and reverse engineering?

Describe the purpose of use case diagram?

How object oriented concepts are related to UML?

Is component diagram representing the dynamic view of a system?

Name major building blocks of UML?

Name some scenarios where object diagrams are used?

Name the three mechanisms in stereotype?

What are the artifacts of a deployment diagram?

What are the artifacts used to make a component diagram?

What are the different UML diagrams?

What are the different elements of a use case diagram?

What are the different modeling used in UML?

What are the elements of an object diagram?

What are the goals of UML?

What are the main usages of a deployment diagram?









What are the notations used in behavioural things?

What are the notations used in relationships?

What are the notations used in structural things?

What are the other four diagrams used in UML for capturing dynamic behaviour of a system?

What are the structural diagrams and behavioural diagrams?

What are the usages of sequence and collaboration diagram?

What do you mean by dynamic behaviour of a system?

What does an object diagram capture?

What is OO analysis?

What is OO design?

What is a Statechart diagram?

What is a class diagram?

What is a constraint rule?

What is a deployment diagram?

What is a node?

What is a reactive system?

What is a state?

What is a use case diagram?

What is an activity diagram?

What is an event and how it influences the states of an object?

What is an interaction diagram?

What is an object diagram?

What is collaboration diagram?

What is component diagram?

What is composition and aggregation?

What is difference between analysis and design?

What is generalization and when it is used?

What is meant by isomorphic?

What is responsibility of an object?

What is role of UML in OO analysis and design?





What is sequence diagram?

What is static and dynamic view of a system?

What is structural diagram?

What is the difference between a class diagram and an object diagram?

What is the difference between a flow chart and an activity diagram?

What is the difference between aggregation and composition?

What is the difference between sequence and collaboration diagram?

What is the interaction diagrams used in UML?

What is the main usage of a Statechart diagram?

What is the main usage of an activity diagram?

What is the only grouping thing available in UML?

Why conceptual model is important?

Why statechart diagram us used?






12/10/14, 1:ML - Overview

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UML Overview

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UML is a standard language for specifying, visualizing, constructing, and documenting the artifacts of

software systems.

UML was created by Object Management Group (OMG) and UML 1.0 specification draft was proposed to

the OMG in January 1997.

OMG is continuously putting effort to make a truly industry standard.

UML stands for Unified Modeling Language.

UML is different from the other common programming languages like C++, Java, COBOL etc.

UML is a pictorial language used to make software blue prints.

So UML can be described as a general purpose visual modeling language to visualize, specify, construct

and document software system. Although UML is generally used to model software systems but it is no

limited within this boundary. It is also used to model non software systems as well like process flow in

manufacturing unit etc.

UML is not a programming language but tools can be used to generate code in various languages using

UML diagrams. UML has a direct relation with object oriented analysis and design. After some

standardization UML is become an OMG (Object Management Group) standard.

Goals of UML:

A picture is worth a thousand words, this absolutely fits while discussing about UML. Object oriented

concepts were introduced much earlier than UML. So at that time there were no standard

methodologies to organize and consolidate the object oriented development. At that point of time UML

came into picture.

There are a number of goals for developing UML but the most important is to define some general

purpose modeling language which all modelers can use and also it needs to be made simple to

understand and use.

UML diagrams are not only made for developers but also for business users, common people andanybody interested to understand the system. The system can be a software or non software. So it

must be clear that UML is not a development method rather it accompanies with processes to make a

successful system.

At the conclusion the goal of UML can be defined as a simple modeling mechanism to model all possible

practical systems in today.s complex environment.

A conceptual model of UML:


http://www.tutorialspoint.com/uml/uml_building_blocks.htm







To understand conceptual model of UML first we need to clarify What is a conceptual model? and Why a

conceptual model is at all required?

A conceptual model can be defined as a model which is made of concepts and their relationships

A conceptual model is the first step before drawing a UML diagram. It helps to understand the

entities in the real world and how they interact with each other.

As UML describes the real time systems it is very important to make a conceptual model and then

proceed gradually. Conceptual model of UML can be mastered by learning the following three majorelements:

UML building blocks

Rules to connect the building blocks

Common mechanisms of UML

Object oriented concepts:

UML can be described as the successor of object oriented analysis and design.

An object contains both data and methods that control the data. The data represents the state of the

object. A class describes an object and they also form hierarchy to model real world system. Thehierarchy is represented as inheritance and the classes can also be associated in different manners as

per the requirement.

The objects are the real world entities that exist around us and the basic concepts like abstraction,

encapsulation, inheritance, polymorphism all can be represented using UML.

So UML is powerful enough to represent all the concepts exists in object oriented analysis and design.

UML diagrams are representation of object oriented concepts only. So before learning UML, it becomes

important to understand OO concepts in details.

Following are some fundamental concepts of object oriented world:

Objects: Objects represent an entity and the basic building block.

Class: Class is the blue print of an object.

Abstraction: Abstraction represents the behavior of an real world entity.

Encapsulation: Encapsulation is the mechanism of binding the data together and hiding them

from outside world.

Inheritance: Inheritance is the mechanism of making new classes from existing one.

Polymorphism: It defines the mechanism to exists in different forms.

OO Analysis and Design

Object Oriented analysis can be defined as investigation and to be more specific it is the investigation

of objects. Design means collaboration of identified objects.

So it is important to understand the OO analysis and design concepts. Now the most important purpose

of OO analysis is to identify objects of a system to be designed. This analysis is also done for an

existing system. Now an efficient analysis is only possible when we are able to start thinking in a way

where objects can be identified. After identifying the objects their relationships are identified and finally





the design is produced.

So the purpose of OO analysis and design can described as:

Identifying the objects of a system.

Identify their relationships.

Make a design which can be converted to executables using OO languages.

There are three basic steps where the OO concepts are applied and implemented. The steps can be

defined as

OO Analysis --> OO Design --> OO implementation using OO languages

Now the above three points can be described in details:

During object oriented analysis the most important purpose is to identify objects and describing

them in a proper way. If these objects are identified efficiently then the next job of design is

easy. The objects should be identified with responsibilities. Responsibilities are the functions

performed by the object. Each and every object has some type of responsibilities to be

performed. When these responsibilities are collaborated the purpose of the system is fulfilled.

The second phase is object oriented design. During this phase emphasis is given upon the

requirements and their fulfilment. In this stage the objects are collaborated according to their

intended association. After the association is complete the design is also complete.

The third phase is object oriented implementation. In this phase the design is implemented using

object oriented languages like Java, C++ etc.

Role of UML in OO design:

UML is a modeling language used to model software and non software systems. Although UML is used

for non software systems the emphasis is on modeling object oriented software applications. Most of

the UML diagrams discussed so far are used to model different aspects like static, dynamic etc. Now

what ever be the aspect the artifacts are nothing but objects.

If we look into class diagram, object diagram, collaboration diagram, interaction diagrams all would

basically be designed based on the objects.

So the relation between OO design and UML is very important to understand. The OO design is

transformed into UML diagrams according to the requirement. Before understanding the UML in details

the OO concepts should be learned properly. Once the OO analysis and design is done the next step is

very easy. The input from the OO analysis and design is the input to the UML diagrams.






12/10/14, 1:ML - Building Blocks

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UML Building Blocks

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As UML describes the real time systems it is very important to make a conceptual model and then

proceed gradually. Conceptual model of UML can be mastered by learning the following three major

elements:

UML building blocks

Rules to connect the building blocks

Common mechanisms of UML

This chapter describes all the UML building blocks. The building blocks of UML can be defined as:

Things

Relationships

Diagrams

(1) Things:

Things are the most important building blocks of UML. Things can be:

Structural

Behavioral

Grouping

Annotational

Structural things:

The Structural things define the static part of the model. They represent physical and conceptual

elements. Following are the brief descriptions of the structural things.

Class:

Class represents set of objects having similar responsibilities.

Interface:

Interface defines a set of operations which specify the responsibility of a class.


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Collaboration:

Collaboration defines interaction between elements.

Use case:

Use case represents a set of actions performed by a system for a specific goal.

Component:

Component describes physical part of a system.

Node:

A node can be defined as a physical element that exists at run time.

Behavioral things:

A behavioral thing consists of the dynamic parts of UML models. Following are the behavioral things:

Interaction:

Interaction is defined as a behavior that consists of a group of messages exchanged among elements t

accomplish a specific task.

State machine:

State machine is useful when the state of an object in its life cycle is important. It defines the sequenc

of states an object goes through in response to events. Events are external factors responsible for stat

change.





Grouping things:

Grouping things can be defined as a mechanism to group elements of a UML model together. There i

only one grouping thing available:

Package:

Package is the only one grouping thing available for gathering structural and behavioral things.

Annotational things:Annotational things can be defined as a mechanism to capture remarks, descriptions, and comments

of UML model elements. Note is the only one Annotational thing available.

Note:

A note is used to render comments, constraints etc of an UML element.

(2) Relationship :

Relationship is another most important building block of UML. It shows how elements are associated

with each other and this association describes the functionality of an application.

There are four kinds of relationships available.

Dependency:

Dependency is a relationship between two things in which change in one element also affects the other

one.

Association:

Association is basically a set of links that connects elements of an UML model. It also describes how

many objects are taking part in that relationship.





Generalization:

Generalization can be defined as a relationship which connects a specialized element with a generalized

element. It basically describes inheritance relationship in the world of objects.

Realization:

Realization can be defined as a relationship in which two elements are connected. One element

describes some responsibility which is not implemented and the other one implements them. This

relationship exists in case of interfaces.

(3) UML Diagrams:

UML diagrams are the ultimate output of the entire discussion. All the elements, relationships are used

to make a complete UML diagram and the diagram represents a system.

The visual effect of the UML diagram is the most important part of the entire process. All the other

elements are used to make it a complete one.

UML includes the following nine diagrams and the details are described in the following chapters.

1. Class diagram

2. Object diagram3. Use case diagram

4. Sequence diagram

5. Collaboration diagram

6. Activity diagram

7. Statechart diagram

8. Deployment diagram

9. Component diagram

We would discuss all these diagrams in subsequent chapters of this tutorial.






12/10/14, 1:ML - Architecture

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UML Architecture

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Any real world system is used by different users. The users can be developers, testers, business people

analysts and many more. So before designing a system the architecture is made with different

perspectives in mind. The most important part is to visualize the system from different viewer.s

perspective. The better we understand the better we make the system.

UML plays an important role in defining different perspectives of a system. These perspectives are:

Design

Implementation

ProcessDeployment

And the centre is the Use Case view which connects all these four. A Use case represents the

functionality of the system. So the other perspectives are connected with use case.

Design of a system consists of classes, interfaces and collaboration. UML provides class diagram

object diagram to support this.

Implementation defines the components assembled together to make a complete physical

system. UML component diagram is used to support implementation perspective.

Process defines the flow of the system. So the same elements as used in Design are also used tsupport this perspective.

Deployment represents the physical nodes of the system that forms the hardware. UML

deployment diagram is used to support this perspective.



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12/10/14, 1:ML - Modeling Types

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UML Modeling Types

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It is very important to distinguish between the UML model. Different diagrams are used for different

type of UML modeling. There are three important type of UML modelings:

Structural modeling:

Structural modeling captures the static features of a system. They consist of the followings:

Classes diagrams

Objects diagramsDeployment diagrams

Package diagrams

Composite structure diagram

Component diagram

Structural model represents the framework for the system and this framework is the place where all

other components exist. So the class diagram, component diagram and deployment diagrams are the

part of structural modeling. They all represent the elements and the mechanism to assemble them.

But the structural model never describes the dynamic behavior of the system. Class diagram is the

most widely used structural diagram.

Behavioral Modeling:

Behavioral model describes the interaction in the system. It represents the interaction among the

structural diagrams. Behavioral modeling shows the dynamic nature of the system. They consist of the

following:

Activity diagrams

Interaction diagrams

Use case diagrams

All the above show the dynamic sequence of flow in a system.

Architectural Modeling:

Architectural model represents the overall framework of the system. It contains both structural and

behavioral elements of the system. Architectural model can be defined as the blue print of the entire

system. Package diagram comes under architectural modeling.

http://www.tutorialspoint.com/uml/uml_basic_notations.htm






12/10/14, 1:ML - Basic Notations

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UML Basic Notations

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UML is popular for its diagrammatic notations. We all know that UML is for visualizing, specifying,

constructing and documenting the components of software and non software systems. Here the

Visualization is the most important part which needs to be understood and remembered by heart.





for things and relationships. And the UML diagrams are made using the notations of things andrelationships. Extensibility is another important feature which makes UML more powerful and flexible.

The chapter describes the UML Basic Notations in more details. This is just an extension to the UML

buildling block section I have discussed in previous chapter.

Structural Things:

Graphical notations used in structural things are the most widely used in UML. These are considered as

the nouns of UML models. Following are the list of structural things.

Classes

InterfaceCollaboration

Use case

Active classes

Components

Nodes

Class Notation:

UML class is represented by the diagram shown below. The diagram is divided into four parts.

The top section is used to name the class.

The second one is used to show the attributes of the class.The third section is used to describe the operations performed by the class.

The fourth section is optional to show any additional components.




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Classes are used to represent objects. Objects can be anything having properties and responsibility.

Object Notation:

The object is represented in the same way as the class. The only difference is the name which is

underlined as shown below.

As object is the actual implementation of a class which is known as the instance of a class. So it has th

same usage as the class.

Interface Notation:

Interface is represented by a circle as shown below. It has a name which is generally written below the

circle.

Interface is used to describe functionality without implementation. Interface is the just like a template





where you define different functions not the implementation. When a class implements the interface it

also implements the functionality as per the requirement.

Collaboration Notation:

Collaboration is represented by a dotted eclipse as shown below. It has a name written inside the

eclipse.

Collaboration represents responsibilities. Generally responsibilities are in a group.

Use case Notation:

Use case is represented as an eclipse with a name inside it. It may contain additional responsibilities.

Use case is used to capture high level functionalities of a system.

Actor Notation:

An actor can be defined as some internal or external entity that interacts with the system.





Actor is used in a use case diagram to describe the internal or external entities.

Initial State Notation:

Initial state is defined to show the start of a process. This notation is used in almost all diagrams.

The usage of Initial State Notation is to show the starting point of a process.

Final State Notation:

Final state is used to show the end of a process. This notation is also used in almost all diagrams to

describe the end.

The usage of Final State Notation is to show the termination point of a process.

Active class Notation:

Active class looks similar to a class with a solid border. Active class is generally used to describe

concurrent behaviour of a system.

Active class is used to represent concurrency in a system.





Component Notation:

A component in UML is shown as below with a name inside. Additional elements can be added whereve

required.

Component is used to represent any part of a system for which UML diagrams are made.

Node Notation:

A node in UML is represented by a square box as shown below with a name. A node represents a

physical component of the system.

Node is used to represent physical part of a system like server, network etc.

Behavioural Things:

Dynamic parts are one of the most important elements in UML. UML has a set of powerful features to

represent the dynamic part of software and non software systems. These features include interactions

and state machines.

Interactions can be of two types:

Sequential (Represented by sequence diagram)

Collaborative (Represented by collaboration diagram)

Interaction Notation:

Interaction is basically message exchange between two UML components. The following diagram

represents different notations used in an interaction.





Interaction is used to represent communication among the components of a system.

State machine Notation:

State machine describes the different states of a component in its life cycle. The notations are

described in the following diagram.





State machine is used to describe different states of a system component. The state can be active, idle

or any other depending upon the situation.

Grouping Things:

Organizing the UML models are one of the most important aspects of the design. In UML there is only

one element available for grouping and that is package.

Package Notation:

Package notation is shown below and this is used to wrap the components of a system.

Annotational Things:

In any diagram explanation of different elements and their functionalities are very important. So UML

has notes notation to support this requirement.

Note Notation:





This notation is shown below and they are used to provide necessary information of a system.

Relationships

A model is not complete unless the relationships between elements are described properly. TheRelationship gives a proper meaning to an UML model. Following are the different types of relationship

available in UML.

Dependency

Association

Generalization

Extensibility

Dependency Notation:

Dependency is an important aspect in UML elements. It describes the dependent elements and the

direction of dependency.

Dependency is represented by a dotted arrow as shown below. The arrow head represents the

independent element and the other end the dependent element.

Dependency is used to represent dependency between two elements of a system.

Association Notation:

Association describes how the elements in an UML diagram are associated. In simple word it describes

how many elements are taking part in an interaction.

Association is represented by a dotted line with (without) arrows on both sides. The two ends represen

two associated elements as shown below. The multiplicity is also mentioned at the ends (1, * etc) to

show how many objects are associated.





Association is used to represent the relationship between two elements of a system.

Generalization Notation:

Generalization describes the inheritance relationship of the object oriented world. It is parent and child

relationship.

Generalization is represented by an arrow with hollow arrow head as shown below. One end represents

the parent element and the other end child element.

Generalization is used to describe parent-child relationship of two elements of a system.

Extensibility Notation:

All the languages (programming or modeling) have some mechanism to extend its capabilities like

syntax, semantics etc. UML is also having the following mechanisms to provide extensibility features.

Stereotypes (Represents new elements)

Tagged values (Represents new attributes)

Constraints (Represents the boundaries)

Extensibility notations are used to enhance the power of the language. It is basically additional

elements used to represent some extra behaviour of the system. These extra behaviours are not

covered by the standard available notations.



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UML Standard Diagrams

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In the previous chapters we have discussed about the building blocks and other necessary elements of

UML. Now we need to understand where to use those elements.

The elements are like components which can be associated in different ways to make a complete UML

pictures which is known as diagram. So it is very important to understand the different diagrams to

implement the knowledge in real life systems.

Any complex system is best understood by making some kind of diagrams or pictures. These diagrams

have a better impact on our understanding. So if we look around then we will realize that the diagrams

are not a new concept but it is used widely in different form in different industries.

We prepare UML diagrams to understand a system in better and simple way. A single diagram is not

enough to cover all aspects of the system. So UML defines various kinds of diagrams to cover most of

the aspects of a system.

You can also create your own set of diagrams to meet your requirements. Diagrams are generally mad

in an incremental and iterative way.

There are two broad caetgories of diagrams and then are again divided into sub-categories:

Structural Diagrams

Behavioral Diagrams

Structural Diagrams:

The structural diagrams represent the static aspect of the system. These static aspects represent those

parts of a diagram which forms the main structure and therefore stable.

These static parts are represents by classes, interfaces, objects, components and nodes. The four

structural diagrams are:

Class diagram

Object diagram

Component diagramDeployment diagram

Class Diagram:

Class diagrams are the most common diagrams used in UML. Class diagram consists of classes,

interfaces, associations and collaboration.

Class diagrams basically represent the object oriented view of a system which is static in nature.

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Active class is used in a class diagram to represent the concurrency of the system.

Class diagram represents the object orientation of a system. So it is generally used for development

purpose. This is the most widely used diagram at the time of system construction.

Object Diagram:

Object diagrams can be described as an instance of class diagram. So these diagrams are more close t

real life scenarios where we implement a system.

Object diagrams are a set of objects and their relationships just like class diagrams and also represent

the static view of the system.

The usage of object diagrams is similar to class diagrams but they are used to build prototype of a

system from practical perspective.

Component Diagram:

Component diagrams represent a set of components and their relationships. These components consist

of classes, interfaces or collaborations.

So Component diagrams represent the implementation view of a system.

During design phase software artifacts (classes, interfaces etc) of a system are arranged in different

groups depending upon their relationship. Now these groups are known as components.

Finally, component diagrams are used to visualize the implementation.

Deployment Diagram:

Deployment diagrams are a set of nodes and their relationships. These nodes are physical entities

where the components are deployed.

Deployment diagrams are used for visualizing deployment view of a system. This is generally used by

the deployment team.

Note: If the above descriptions and usages are observed carefully then it is very clear that all the

diagrams are having some relationship with one another. Component diagrams are dependent upon the

classes, interfaces etc which are part of class/object diagram. Again the deployment diagram is

dependent upon the components which are used to make a component diagrams.

Behavioral Diagrams:

Any system can have two aspects, static and dynamic. So a model is considered as complete when bot

the aspects are covered fully.

Behavioral diagrams basically capture the dynamic aspect of a system. Dynamic aspect can be furtherdescribed as the changing/moving parts of a system.

UML has the following five types of behavioral diagrams:

Use case diagram

Sequence diagram

Collaboration diagram

Statechart diagram

Activity diagram





Use case Diagram:

Use case diagrams are a set of use cases, actors and their relationships. They represent the use case

view of a system.

A use case represents a particular functionality of a system.

So use case diagram is used to describe the relationships among the functionalities and their

internal/external controllers. These controllers are known as actors.

Sequence Diagram:

A sequence diagram is an interaction diagram. From the name it is clear that the diagram deals with

some sequences, which are the sequence of messages flowing from one object to another.

Interaction among the components of a system is very important from implementation and execution

perspective.

So Sequence diagram is used to visualize the sequence of calls in a system to perform a specific

functionality.

Collaboration Diagram:Collaboration diagram is another form of interaction diagram. It represents the structural organization

of a system and the messages sent/received. Structural organization consists of objects and links.

The purpose of collaboration diagram is similar to sequence diagram. But the specific purpose of

collaboration diagram is to visualize the organization of objects and their interaction.

Statechart Diagram:

Any real time system is expected to be reacted by some kind of internal/external events. These events

are responsible for state change of the system.

Statechart diagram is used to represent the event driven state change of a system. It basicallydescribes the state change of a class, interface etc.

State chart diagram is used to visualize the reaction of a system by internal/external factors.

Activity Diagram:

Activity diagram describes the flow of control in a system. So it consists of activities and links. The flow

can be sequential, concurrent or branched.

Activities are nothing but the functions of a system. Numbers of activity diagrams are prepared to

capture the entire flow in a system.

Activity diagrams are used to visualize the flow of controls in a system. This is prepared to have an ideof how the system will work when executed.

Note: Dynamic nature of a system is very difficult to capture. So UML has provided features to capture

the dynamics of a system from different angles. Sequence diagrams and collaboration diagrams are

isomorphic so they can be converted from one another without losing any information. This is also true

for statechart and activity diagram.



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UML Class Diagram

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Overview:

The class diagram is a static diagram. It represents the static view of an application. Class diagram is

not only used for visualizing, describing and documenting different aspects of a system but also for

constructing executable code of the software application.

The class diagram describes the attributes and operations of a class and also the constraints imposed

on the system. The class diagrams are widely used in the modelling of object oriented systems becaus

they are the only UML diagrams which can be mapped directly with object oriented languages.

The class diagram shows a collection of classes, interfaces, associations, collaborations and constraints

It is also known as a structural diagram.

Purpose:

The purpose of the class diagram is to model the static view of an application. The class diagrams are

the only diagrams which can be directly mapped with object oriented languages and thus widely used

at the time of construction.

The UML diagrams like activity diagram, sequence diagram can only give the sequence flow of the

application but class diagram is a bit different. So it is the most popular UML diagram in the coder

community.

So the purpose of the class diagram can be summarized as:

Analysis and design of the static view of an application.

Describe responsibilities of a system.

Base for component and deployment diagrams.

Forward and reverse engineering.

How to draw Class Diagram?

Class diagrams are the most popular UML diagrams used for construction of software applications. So i

is very important to learn the drawing procedure of class diagram.

Class diagrams have lot of properties to consider while drawing but here the diagram will be considered

from a top level view.

Class diagram is basically a graphical representation of the static view of the system and represents

different aspects of the application. So a collection of class diagrams represent the whole system.

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The following points should be remembered while drawing a class diagram:

The name of the class diagram should be meaningful to describe the aspect of the system.

Each element and their relationships should be identified in advance.

Responsibility (attributes and methods) of each class should be clearly identified.

For each class minimum number of properties should be specified. Because unnecessary

properties will make the diagram complicated.

Use notes when ever required to describe some aspect of the diagram. Because at the end of the

drawing it should be understandable to the developer/coder.

Finally, before making the final version, the diagram should be drawn on plain paper and rework

as many times as possible to make it correct.

Now the following diagram is an example of an Order System of an application. So it describes a

particular aspect of the entire application.

First of all Order and Customer are identified as the two elements of the system and they have a

one to many relationship because a customer can have multiple orders.

We would keep Order class is an abstract class and it has two concrete classes (inheritance

relationship) SpecialOrder and NormalOrder .

The two inherited classes have all the properties as the Order class. In addition they have

additional functions like dispatch () and receive ().

So the following class diagram has been drawn considering all the points mentioned above:





Where to use Class Diagrams?

Class diagram is a static diagram and it is used to model static view of a system. The static view

describes the vocabulary of the system.

Class diagram is also considered as the foundation for component and deployment diagrams. Class

diagrams are not only used to visualize the static view of the system but they are also used to

construct the executable code for forward and reverse engineering of any system.

Generally UML diagrams are not directly mapped with any object oriented programming languages but

the class diagram is an exception.

Class diagram clearly shows the mapping with object oriented languages like Java, C++ etc. So from

practical experience class diagram is generally used for construction purpose.

So in a brief, class diagrams are used for:

Describing the static view of the system.

Showing the collaboration among the elements of the static view.

Describing the functionalities performed by the system.

Construction of software applications using object oriented languages.






12/10/14, 1:ML - Component Diagrams

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UML Component Diagram

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Overview:

Component diagrams are different in terms of nature and behaviour. Component diagrams are used to

model physical aspects of a system.

Now the question is what are these physical aspects? Physical aspects are the elements like

executables, libraries, files, documents etc which resides in a node.

So component diagrams are used to visualize the organization and relationships among components in

a system. These diagrams are also used to make executable systems.

Purpose:

Component diagram is a special kind of diagram in UML. The purpose is also different from all other

diagrams discussed so far. It does not describe the functionality of the system but it describes the

components used to make those functionalities.

So from that point component diagrams are used to visualize the physical components in a system.

These components are libraries, packages, files etc.

Component diagrams can also be described as a static implementation view of a system. Static

implementation represents the organization of the components at a particular moment.

A single component diagram cannot represent the entire system but a collection of diagrams are used

to represent the whole.

So the purpose of the component diagram can be summarized as:

Visualize the components of a system.

Construct executables by using forward and reverse engineering.

Describe the organization and relationships of the components.

How to draw Component Diagram?

Component diagrams are used to describe the physical artifacts of a system. This artifact includes files

executables, libraries etc.

So the purpose of this diagram is different, Component diagrams are used during the implementation

phase of an application. But it is prepared well in advance to visualize the implementation details.

Initially the system is designed using different UML diagrams and then when the artifacts are ready

component diagrams are used to get an idea of the implementation.


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This diagram is very important because without it the application cannot be implemented efficiently. A

well prepared component diagram is also important for other aspects like application performance,

maintenance etc.

So before drawing a component diagram the following artifacts are to be identified clearly:

Files used in the system.

Libraries and other artifacts relevant to the application.

Relationships among the artifacts.

Now after identifying the artifacts the following points needs to be followed:

Use a meaningful name to identify the component for which the diagram is to be drawn.

Prepare a mental layout before producing using tools.

Use notes for clarifying important points.

The following is a component diagram for order management system. Here the artifacts are files. So

the diagram shows the files in the application and their relationships. In actual the component diagram

also contains dlls, libraries, folders etc.

In the following diagram four files are identified and their relationships are produced. Component

diagram cannot be matched directly with other UML diagrams discussed so far. Because it is drawn for

completely different purpose.

So the following component diagram has been drawn considering all the points mentioned above:

Where to use Component Diagrams?





We have already described that component diagrams are used to visualize the static implementation

view of a system. Component diagrams are special type of UML diagrams used for different purposes.

These diagrams show the physical components of a system. To clarify it, we can say that component

diagrams describe the organization of the components in a system.

Organization can be further described as the location of the components in a system. These

components are organized in a special way to meet the system requirements.

As we have already discussed those components are libraries, files, executables etc. Now beforeimplementing the application these components are to be organized. This component organization is

also designed separately as a part of project execution.

Component diagrams are very important from implementation perspective. So the implementation

team of an application should have a proper knowledge of the component details.

Now the usage of component diagrams can be described as:

Model the components of a system.

Model database schema.

Model executables of an application.

Model system's source code.






12/10/14, 1:ML - Object Diagrams

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UML Object Diagram

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Overview:

Object diagrams are derived from class diagrams so object diagrams are dependent upon class

diagrams.

Object diagrams represent an instance of a class diagram. The basic concepts are similar for class

diagrams and object diagrams. Object diagrams also represent the static view of a system but this

static view is a snapshot of the system at a particular moment.

Object diagrams are used to render a set of objects and their relationships as an instance.

Purpose:

The purpose of a diagram should be understood clearly to implement it practically. The purposes of

object diagrams are similar to class diagrams.

The difference is that a class diagram represents an abstract model consisting of classes and their

relationships. But an object diagram represents an instance at a particular moment which is concrete in

nature.

It means the object diagram is more close to the actual system behaviour. The purpose is to capture

the static view of a system at a particular moment.

So the purpose of the object diagram can be summarized as:


Object relationships of a system

Static view of an interaction.

Understand object behaviour and their relationship from practical perspective

How to draw Object Diagram?

We have already discussed that an object diagram is an instance of a class diagram. It implies that anobject diagram consists of instances of things used in a class diagram.

So both diagrams are made of same basic elements but in different form. In class diagram elements

are in abstract form to represent the blue print and in object diagram the elements are in concrete form

to represent the real world object.

To capture a particular system, numbers of class diagrams are limited. But if we consider object

diagrams then we can have unlimited number of instances which are unique in nature. So only those

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instances are considered which are having impact on the system.

From the above discussion it is clear that a single object diagram cannot capture all the necessary

instances or rather cannot specify all objects of a system. So the solution is:

First, analyze the system and decide which instances are having important data and association.

Second, consider only those instances which will cover the functionality.

Third, make some optimization as the numbers of instances are unlimited.

Before drawing an object diagrams the following things should be remembered and understood clearly

Object diagrams are consist of objects.

The link in object diagram is used to connect objects.

Objects and links are the two elements used to construct an object diagram.

Now after this the following things are to be decided before starting the construction of the diagram:

The object diagram should have a meaningful name to indicate its purpose.

The most important elements are to be identified.

The association among objects should be clarified.

Values of different elements need to be captured to include in the object diagram.

Add proper notes at points where more clarity is required.

The following diagram is an example of an object diagram. It represents the Order management systemwhich we have discussed in Class Diagram. The following diagram is an instance of the system at a

particular time of purchase. It has the following objects

Customer

Order

SpecialOrder

NormalOrder

Now the customer object (C) is associated with three order objects (O1, O2 and O3). These order

objects are associated with special order and normal order objects (S1, S2 and N1). The customer is

having the following three orders with different numbers (12, 32 and 40) for the particular time

considered.

Now the customer can increase number of orders in future and in that scenario the object diagram willreflect that. If order, special order and normal order objects are observed then we you will find that

they are having some values.

For orders the values are 12, 32, and 40 which implies that the objects are having these values for the

particular moment (here the particular time when the purchase is made is considered as the moment)

when the instance is captured.

The same is for special order and normal order objects which are having number of orders as 20, 30

and 60. If a different time of purchase is considered then these values will change accordingly.





12/10/14, 1:ML - Deployment Diagrams

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UML Deployment Diagram

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Overview:

Deployment diagrams are used to visualize the topology of the physical components of a system where

the software components are deployed.

So deployment diagrams are used to describe the static deployment view of a system. Deployment

diagrams consist of nodes and their relationships.

Purpose:

The name Deployment itself describes the purpose of the diagram. Deployment diagrams are used for

describing the hardware components where software components are deployed. Component diagrams

and deployment diagrams are closely related.

Component diagrams are used to describe the components and deployment diagrams shows how they

are deployed in hardware.

UML is mainly designed to focus on software artifacts of a system. But these two diagrams are special

diagrams used to focus on software components and hardware components.

So most of the UML diagrams are used to handle logical components but deployment diagrams are

made to focus on hardware topology of a system. Deployment diagrams are used by the system

engineers.

The purpose of deployment diagrams can be described as:

Visualize hardware topology of a system.

Describe the hardware components used to deploy software components.

Describe runtime processing nodes.

How to draw Deployment Diagram?

Deployment diagram represents the deployment view of a system. It is related to the component

diagram. Because the components are deployed using the deployment diagrams. A deployment

diagram consists of nodes. Nodes are nothing but physical hardwares used to deploy the application.

Deployment diagrams are useful for system engineers. An efficient deployment diagram is very

important because it controls the following parameters

Performance

Scalability


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Maintainability

Portability

So before drawing a deployment diagram the following artifacts should be identified:

Nodes

Relationships among nodes

The following deployment diagram is a sample to give an idea of the deployment view of order

management system. Here we have shown nodes as:

Monitor

Modem

Caching server

Server

The application is assumed to be a web based application which is deployed in a clustered environment

using server 1, server 2 and server 3. The user is connecting to the application using internet. Thecontrol is flowing from the caching server to the clustered environment.

So the following deployment diagram has been drawn considering all the points mentioned above:

Where to use Deployment Diagrams?





Deployment diagrams are mainly used by system engineers. These diagrams are used to describe the

physical components (hardwares), their distribution and association.

To clarify it in details we can visualize deployment diagrams as the hardware components/nodes on

which software components reside.

Software applications are developed to model complex business processes. Only efficient software

applications are not sufficient to meet business requirements. Business requirements can be described

as to support increasing number of users, quick response time etc.

To meet these types of requirements hardware components should be designed efficiently and in a cos

effective way.

Now a day's software applications are very complex in nature. Software applications can be stand

alone, web based, distributed, mainframe based and many more. So it is very important to design the

hardware components efficiently.

So the usage of deployment diagrams can be described as follows:

To model the hardware topology of a system.

To model embedded system.

To model hardware details for a client/server system.

To model hardware details of a distributed application.







12/10/14, 1:ML - Use Case Diagrams

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UML Use Case Diagram

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Overview:

To model a system the most important aspect is to capture the dynamic behaviour. To clarify a bit in

details, dynamic behaviour means the behaviour of the system when it is running /operating.

So only static behaviour is not sufficient to model a system rather dynamic behaviour is more importan

than static behaviour. In UML there are five diagrams available to model dynamic nature and use case

diagram is one of them. Now as we have to discuss that the use case diagram is dynamic in nature

there should be some internal or external factors for making the interaction.

These internal and external agents are known as actors. So use case diagrams are consists of actors,

use cases and their relationships. The diagram is used to model the system/subsystem of an

application. A single use case diagram captures a particular functionality of a system.

So to model the entire system numbers of use case diagrams are used.

Purpose:

The purpose of use case diagram is to capture the dynamic aspect of a system. But this definition is to

generic to describe the purpose.

Because other four diagrams (activity, sequence, collaboration and Statechart) are also having the

same purpose. So we will look into some specific purpose which will distinguish it from other four

diagrams.

Use case diagrams are used to gather the requirements of a system including internal and external

influences. These requirements are mostly design requirements. So when a system is analyzed to

gather its functionalities use cases are prepared and actors are identified.

Now when the initial task is complete use case diagrams are modelled to present the outside view.

So in brief, the purposes of use case diagrams can be as follows:

Used to gather requirements of a system.

Used to get an outside view of a system.

Identify external and internal factors influencing the system.

Show the interacting among the requirements are actors.

How to draw Use Case Diagram?

Use case diagrams are considered for high level requirement analysis of a system. So when the


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requirements of a system are analyzed the functionalities are captured in use cases.

So we can say that uses cases are nothing but the system functionalities written in an organized

manner. Now the second things which are relevant to the use cases are the actors. Actors can be

defined as something that interacts with the system.

The actors can be human user, some internal applications or may be some external applications. So in

a brief when we are planning to draw an use case diagram we should have the following items

identified.

Functionalities to be represented as an use case

Actors

Relationships among the use cases and actors.

Use case diagrams are drawn to capture the functional requirements of a system. So after identifying

the above items we have to follow the following guidelines to draw an efficient use case diagram.

The name of a use case is very important. So the name should be chosen in such a way so that i

can identify the functionalities performed.

Give a suitable name for actors.

Show relationships and dependencies clearly in the diagram.

Do not try to include all types of relationships. Because the main purpose of the diagram is to

identify requirements.

Use note when ever required to clarify some important points.

The following is a sample use case diagram representing the order management system. So if we look

into the diagram then we will find three use cases (Order, SpecialOrder and NormalOrder) and one

actor which is customer.

The SpecialOrder and NormalOrder use cases are extended from Order use case. So they have extends

relationship. Another important point is to identify the system boundary which is shown in the picture.

The actor Customer lies outside the system as it is an external user of the system.





Where to Use Case Diagrams?

As we have already discussed there are five diagrams in UML to model dynamic view of a system. Now

each and every model has some specific purpose to use. Actually these specific purposes are different

angles of a running system.

So to understand the dynamics of a system we need to use different types of diagrams. Use case

diagram is one of them and its specific purpose is to gather system requirements and actors.

Use case diagrams specify the events of a system and their flows. But use case diagram never

describes how they are implemented. Use case diagram can be imagined as a black box where only the

input, output and the function of the black box is known.

These diagrams are used at a very high level of design. Then this high level design is refined again and

again to get a complete and practical picture of the system. A well structured use case also describes

the pre condition, post condition, exceptions. And these extra elements are used to make test cases

when performing the testing.

Although the use cases are not a good candidate for forward and reverse engineering but still they are

used in a slight different way to make forward and reverse engineering. And the same is true for

reverse engineering. Still use case diagram is used differently to make it a candidate for reverse

engineering.

In forward engineering use case diagrams are used to make test cases and in reverse engineering use

cases are used to prepare the requirement details from the existing application.

So the following are the places where use case diagrams are used:

Requirement analysis and high level design.

Model the context of a system.

Reverse engineering.



12/10/14, 1:ML - Interaction Diagrams

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UML Interaction Diagram

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Overview:

From the name Interaction it is clear that the diagram is used to describe some type of interactions

among the different elements in the model. So this interaction is a part of dynamic behaviour of the

system.

This interactive behaviour is represented in UML by two diagrams known as Sequence diagram and

Collaboration diagram. The basic purposes of both the diagrams are similar.

Sequence diagram emphasizes on time sequence of messages and collaboration diagram emphasizeson the structural organization of the objects that send and receive messages.

Purpose:

The purposes of interaction diagrams are to visualize the interactive behaviour of the system. Now

visualizing interaction is a difficult task. So the solution is to use different types of models to capture

the different aspects of the interaction.

That is why sequence and collaboration diagrams are used to capture dynamic nature but from a

different angle.

So the purposes of interaction diagram can be describes as:

To capture dynamic behaviour of a system.

To describe the message flow in the system.

To describe structural organization of the objects.

To describe interaction among objects.

How to draw Interaction Diagram?

As we have already discussed that the purpose of interaction diagrams are to capture the dynamic

aspect of a system. So to capture the dynamic aspect we need to understand what a dynamic aspect is

and how it is visualized. Dynamic aspect can be defined as the snap shot of the running system at a

particular moment.

We have two types of interaction diagrams in UML. One is sequence diagram and the other is a

collaboration diagram. The sequence diagram captures the time sequence of message flow from one

object to another and the collaboration diagram describes the organization of objects in a system takin

part in the message flow.

So the following things are to identified clearly before drawing the interaction diagram:

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Objects taking part in the interaction.

Message flows among the objects.

The sequence in which the messages are flowing.

Object organization.

Following are two interaction diagrams modeling order management system. The first diagram is a

sequence diagram and the second is a collaboration diagram.

The Sequence Diagram:

The sequence diagram is having four objects (Customer, Order, SpecialOrder and NormalOrder).

The following diagram has shown the message sequence for SpecialOrder object and the same can be

used in case of NormalOrder object. Now it is important to understand the time sequence of message

flows. The message flow is nothing but a method call of an object.

The first call is sendOrder () which is a method of Order object. The next call is confirm () which is a

method of SpecialOrder object and the last call is Dispatch () which is a method of SpecialOrder object

So here the diagram is mainly describing the method calls from one object to another and this is also

the actual scenario when the system is running.

The Collaboration Diagram:

The second interaction diagram is collaboration diagram. It shows the object organization as shown

below. Here in collaboration diagram the method call sequence is indicated by some numbering

technique as shown below. The number indicates how the methods are called one after another. We

have taken the same order management system to describe the collaboration diagram.

The method calls are similar to that of a sequence diagram. But the difference is that the sequence





diagram does not describe the object organization where as the collaboration diagram shows the objecorganization.

Now to choose between these two diagrams the main emphasis is given on the type of requirement. If

the time sequence is important then sequence diagram is used and if organization is required then

collaboration diagram is used.

Where to use Interaction Diagrams?

We have already discussed that interaction diagrams are used to describe dynamic nature of a system.

Now we will look into the practical scenarios where these diagrams are used. To understand the

practical application we need to understand the basic nature of sequence and collaboration diagram.

The main purposes of both the diagrams are similar as they are used to capture the dynamic behaviouof a system. But the specific purposes are more important to clarify and understood.

Sequence diagrams are used to capture the order of messages flowing from one object to another. And

the collaboration diagrams are used to describe the structural organizations of the objects taking part i

the interaction. A single diagram is not sufficient to describe the dynamic aspect of an entire system so

a set of diagrams are used to capture is as a whole.

The interaction diagrams are used when we want to understand the message flow and the structural

organization. Now message flow means the sequence of control flow from one object to another and

structural organization means the visual organization of the elements in a system.

In a brief the following are the usages of interaction diagrams:

To model flow of control by time sequence.

To model flow of control by structural organizations.

For forward engineering.

For reverse engineering.





12/10/14, 1:ML - Statechart Diagrams

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Before drawing a Statechart diagram we must have clarified the following points:

Identify important objects to be analyzed.

Identify the states.

Identify the events.

The following is an example of a Statechart diagram where the state of Order object is analyzed.

The first state is an idle state from where the process starts. The next states are arrived for events like

send request , confirm request , and dispatch order . These events are responsible for state changes of

order object.

During the life cycle of an object (here order object) it goes through the following states and there may

be some abnormal exists also. This abnormal exit may occur due to some problem in the system. Whe

the entire life cycle is complete it is considered as the complete transaction as mentioned below.

The initial and final state of an object is also shown below.

Where to use Statechart Diagrams?

From the above discussion we can define the practical applications of a Statechart diagram. Statechartdiagrams are used to model dynamic aspect of a system like other four diagrams disused in this

tutorial. But it has some distinguishing characteristics for modeling dynamic nature.

Statechart diagram defines the states of a component and these state changes are dynamic in nature.

So its specific purpose is to define state changes triggered by events. Events are internal or external

factors influencing the system.

Statechart diagrams are used to model states and also events operating on the system. When

implementing a system it is very important to clarify different states of an object during its life time an



12/10/14, 1:ML - Statechart Diagrams

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statechart diagrams are used for this purpose. When these states and events are identified they areused to model it and these models are used during implementation of the system.

If we look into the practical implementation of Statechart diagram then it is mainly used to analyze the

object states influenced by events. This analysis is helpful to understand the system behaviour during

its execution.

So the main usages can be described as:

To model object states of a system.

To model reactive system. Reactive system consists of reactive objects.

To identify events responsible for state changes.







12/10/14, 1:ML - Activity Diagrams

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UML Activity Diagram

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Overview:

Activity diagram is another important diagram in UML to describe dynamic aspects of the system.

Activity diagram is basically a flow chart to represent the flow form one activity to another activity. The

activity can be described as an operation of the system.

So the control flow is drawn from one operation to another. This flow can be sequential, branched or

concurrent. Activity diagrams deals with all type of flow control by using different elements like fork,

join etc.

Purpose:

The basic purposes of activity diagrams are similar to other four diagrams. It captures the dynamic

behaviour of the system. Other four diagrams are used to show the message flow from one object to

another but activity diagram is used to show message flow from one activity to another.

Activity is a particular operation of the system. Activity diagrams are not only used for visualizing

dynamic nature of a system but they are also used to construct the executable system by using forwar

and reverse engineering techniques. The only missing thing in activity diagram is the message part.

It does not show any message flow from one activity to another. Activity diagram is some time

considered as the flow chart. Although the diagrams looks like a flow chart but it is not. It shows

different flow like parallel, branched, concurrent and single.

So the purposes can be described as:

Draw the activity flow of a system.

Describe the sequence from one activity to another.

Describe the parallel, branched and concurrent flow of the system.

How to draw Activity Diagram?

Activity diagrams are mainly used as a flow chart consists of activities performed by the system. But

activity diagram are not exactly a flow chart as they have some additional capabilities. These additiona

capabilities include branching, parallel flow, swimlane etc.

Before drawing an activity diagram we must have a clear understanding about the elements used in

activity diagram. The main element of an activity diagram is the activity itself. An activity is a function

performed by the system. After identifying the activities we need to understand how they are

associated with constraints and conditions.







So before drawing an activity diagram we should identify the following elements:

Activities

Association

Conditions

Constraints

Once the above mentioned parameters are identified we need to make a mental layout of the entire

flow. This mental layout is then transformed into an activity diagram.

The following is an example of an activity diagram for order management system. In the diagram four

activities are identified which are associated with conditions. One important point should be clearly

understood that an activity diagram cannot be exactly matched with the code. The activity diagram is

made to understand the flow of activities and mainly used by the business users.

The following diagram is drawn with the four main activities:

Send order by the customer

Receipt of the order

Confirm order

Dispatch order

After receiving the order request condition checks are performed to check if it is normal or special

order. After the type of order is identified dispatch activity is performed and that is marked as the

termination of the process.

Where to use Activity Diagrams?





The basic usage of activity diagram is similar to other four UML diagrams. The specific usage is to

model the control flow from one activity to another. This control flow does not include messages.

The activity diagram is suitable for modeling the activity flow of the system. An application can have

multiple systems. Activity diagram also captures these systems and describes flow from one system to

another. This specific usage is not available in other diagrams. These systems can be database,

external queues or any other system.

Now we will look into the practical applications of the activity diagram. From the above discussion it is

clear that an activity diagram is drawn from a very high level. So it gives high level view of a system.

This high level view is mainly for business users or any other person who is not a technical person.

This diagram is used to model the activities which are nothing but business requirements. So the

diagram has more impact on business understanding rather implementation details.

Following are the main usages of activity diagram:

Modeling work flow by using activities.

Modeling business requirements.

High level understanding of the system's functionalities.

Investigate business requirements at a later stage.









UML Quick Guide ( Summary )

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UML Overview:

UML is a general purpose modeling language. It was initially started to capture the behavior of complex

software and non software system and now it has become an OMG standard.

UML provides elements and components to support the requirement of complex systems. UML follows

the object oriented concepts and methodology. So object oriented systems are generally modeled usin

the pictorial language.

UML diagrams are drawn from different perspectives like design, implementation, deployment etc.

At the conclusion UML can be defined as a modeling language to capture the architectural, behavioral

and structural aspects of a system.

Objects are the key to this object oriented world. The basic requirement of object oriented analysis and

design is to identify the object efficiently. After that the responsibilities are assigned to the objects.

Once this task is complete the design is done using the input from analysis.

The UML has an important role in this OO analysis and design, The UML diagrams are used to model th

design. So the UML has an important role to play.

UML notations:





for things and relationships. And the UML diagrams are made using the notations of things and

relationships. Extensibility is another important feature which makes UML more powerful and flexible.

UML Diagrams:

Diagrams are the heart of UML. These diagrams are broadly categorized as structural and behavioral

diagrams.

Structural diagrams are consists of static diagrams like class diagram, object diagram etc.

Behavioral diagrams are consists of dynamic diagrams like sequence diagram, collaboration

diagram etc.

The static and dynamic nature of a system is visualized by using these diagrams.

Class diagrams:









Class diagrams are the most popular UML diagrams used by the object oriented community. It

describes the objects in a system and their relationships. Class diagram consists of attributes and

functions.

A single class diagram describes a specific aspect of the system and the collection of class diagrams

represents the whole system. Basically the class diagram represents the static view of a system.

Class diagrams are the only UML diagrams which can be mapped directly with object oriented

languages. So it is widely used by the developer community.

Object Diagram:

An object diagram is an instance of a class diagram. So the basic elements are similar to a class

diagram. Object diagrams are consists of objects and links. It captures the instance of the system at a

particular moment.

Object diagrams are used for prototyping, reverse engineering and modeling practical scenarios.

Component Diagram:

Component diagrams are special kind of UML diagram to describe static implementation view of a

system. Component diagrams consist of physical components like libraries, files, folders etc.

This diagram is used from implementation perspective. More than one component diagrams are used to

represent the entire system. Forward and reverse engineering techniques are used to make executable

from component diagrams.

Deployment Diagram:

Component diagrams are used to describe the static deployment view of a system. These diagrams are

mainly used by system engineers.

Deployment diagrams are consists of nodes and their relationships. An efficient deployment diagram is

an integral part of software application development.

Use Case Diagram;

Use case diagram is used to capture the dynamic nature of a system. It consists of use cases, actors

and their relationships. Use case diagram is used at a high level design to capture the requirements of

a system.

So it represents the system functionalities and their flow. Although the use case diagrams are not a

good candidate for forward and reverse engineering but still they are used in a slightly differently way

to model it.

Interaction Diagram:

Interaction diagrams are used for capturing dynamic nature of a system. Sequence and collaboration

diagrams are the interaction diagrams used for this purpose.

Sequence diagrams are used to capture time ordering of message flow and collaboration diagrams are

used to understand the structural organization of the system. Generally a set of sequence and

collaboration diagrams are used to model an entire system.

Statechart Diagram:





Statechart diagrams are one of the five diagrams used for modeling dynamic nature of a system. These

diagrams are used to model the entire life cycle of an object. Activity diagram is a special kind of

Statechart diagram.

State of an object is defined as the condition where an object resides for a particular time and the

object again moves to other states when some events occur. Statechart diagrams are also used for

forward and reverse engineering.

Activity Diagram:Activity diagram is another important diagram to describe dynamic behaviour. Activity diagram consist

of activities, links, relationships etc. It models all types of flows like parallel, single, concurrent etc.

Activity diagram describes the flow control from one activity to another without any messages. These

diagrams are used to model high level view of business requirements.




12/10/14, 1:ML 2.0 - Overview

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UML 2.0 - Overview

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Overview:

UML 2.0 is totally a different dimension in the world of Unified Modeling Language. It is more complex

and extensive in nature.

The extent of documentation has also increased compared to UML 1.5 version. UML 2.0 also added new

features so that its usage can be more extensive.

UML 2.0 adds the definition of formal and completely defined semantics. This new possibility can beutilized for the development of models and the corresponding systems can be generated from these

models. But to utilize this new dimension a considerable effort has to be made to acquire the

knowledge.

New dimensions in UML2.0:

The structure and documentation of UML was completely revised in the latest version of UML2.0. There

are now two documents available that describe UML:

UML 2.0 Infrastructure defines the basic constructs of the language on which UML is based. This

section is not directly relevant to the users of UML. This is directed more towards the developers

of modeling tools. So this area is not in the scope of this tutorial.

UML 2.0 Superstructure defines the user constructs of UML 2.0. It means those elements of UML

that users will use at the immediate level. So this is the main focus for the user community of

UML.

This revision of UML was created to fulfil a goal to restructure and refine UML so that usability,

implementation, and adaptation are simplified.

The UML infrastructure is used to:

Provide a reusable meta-language core. This is used to define UML itself.

Provide mechanisms to adjustment the language.

The UML superstructure is used to:

Provide better support for component-based development.

Improve constructs for the specification of architectur.

e



12/10/14, 1:ML 2.0 - Overview


Provide better options for the modeling of behaviour.

So the important point to note is the major divisions described above. These divisions are used to

increase the usability of UML and define a clear understanding of its usage.

There is another dimension which is already proposed in this new version. It is a proposal for a

completely new Object Constraint Language (OCL) and Diagram Interchange. These features all

together form the complete UML2.0 package.

Modeling diagrams in UML2.0:

Modeling Interactions:

The interaction diagrams described in UML2.0 is different than the earlier versions. But the basic

concept remains same as the earlier version. The major difference is the enhancement and additional

features added to the diagrams in UML2.0.

UML2.0 models object interaction in the following four different ways.

Sequence diagram is a time dependent view of the interaction between objects to accomplish a

behavioral goal of the system. The time sequence is similar to the earlier version of sequence

diagram. An interaction may be designed at any level of abstraction within the system design,from subsystem interactions to instance-level.

Communication diagram is a new name added in UML2.0. A Communication diagram is a

structural view of the messaging between objects, taken from the Collaboration diagram concept

of UML 1.4 and earlier versions. This can be defined as a modified version of collaboration

diagram.

Interaction Overview diagram is also a new addition in UML2.0. An Interaction Overview

diagram describes a high-level view of a group of interactions combined into a logic sequence,

including flow-control logic to navigate between the interactions.

Timing diagram is also added in UML2.0. It is an optional diagram designed to specify the timeconstraints on messages sent and received in the course of an interaction.

So from the above description it is important to note that the purposes of all the diagrams are to

send/receive messages. Now the handlings of these messages are internal to the objects. So the

objects are also having options to receive and send messages, and here comes another important

aspect called interface. Now these interfaces are responsible for accepting and sending messages to

one another.

So from the above discussion it can be concluded that the interactions in UML2.0 are described in a

different way and that is why the new diagram names have come into picture. But if we analyze the

new diagrams then it is clear that all the diagrams are created based upon the interaction diagrams

described in the earlier versions. The only difference is the additional features added in UML2.0 to mak

the diagrams more efficient and purpose oriented.

Modeling Collaborations:

As we have already discussed that collaboration is used to model common interactions between

objects. To clarify it, we can say that collaboration is a interaction where a set of messages are handled

by a set of objects having pre defined roles.

The important point to note is the difference between the collaboration diagram in earlier version and i



12/10/14, 1:ML 2.0 - Overview


UML2.0 version. So to distinguish the collaboration diagram the name has been changed in UML2.0. InUML2.0 it is named as Communication diagram.

Consequently collaboration is defined as a class with attributes (properties) and behavior (operations).

Compartments on the collaboration class can user defined also and may be used for interactions

(Sequence diagrams) and the structural elements (Composite Structure diagram).

Figure below models the Observer design pattern as collaboration between an object in the role of an

observable item and any number of objects as the observers.

Modeling Communication:

Communication diagram is slightly different than the collaboration diagrams of the earlier versions. We

can say it is a scaled back version of the earlier UML versions. The distinguishing factor of the

communication diagram is the link between objects.

This is a visual link and it is missing in sequence diagram. In sequence diagram only the messages

passed between objects are shown even if there is no link between them.

The Communication diagram is used to prevent the modeler from making this mistake by using an

Object diagram format as the basis for messaging. Each object on a Communication diagram is called

an object lifeline.

The message types in a Communication diagram are the same as in a Sequence diagram. A

Communication diagram may model synchronous, asynchronous, return, lost, found, and object-

creation messages.

Figure below shows an Object diagram with three objects and two links that form the basis for the

Communication diagram. Each object on a Communication diagram is called an object lifeline.



12/10/14, 1:ML 2.0 - Overview


Modeling an Interaction Overview:

In practical usage, a sequence diagram is used to model a single scenario. So numbers of sequence

diagrams are used to complete the entire application. So while modeling a single scenario it is possible

to forget the total process and this can introduce errors.

So to solve this issue the new interaction overview diagram combines the flow of control from an

activity diagram and messaging specification from the sequence diagram.

Activity diagram uses activities and object flows to describe a process. The Interaction Overview

diagram uses interactions and interaction occurrences. The lifelines and messages found in Sequence

diagrams appear only within the interactions or interaction occurrences. However, the lifelines (objects

that participate in the Interaction Overview diagram may be listed along with the diagram name.

Figure below shows an interaction overview diagram with decision diamonds, frames and termination

point



12/10/14, 1:ML 2.0 - Overview


Modeling a Timing Diagram:

The name of this diagram itself describes the purpose of the diagram. It basically deals with the time o

the events over its entire lifecycle.

So a timing diagram can be defined as a special purpose interaction diagram made to focus on the

events of an object in its life time. It is basically a mixture of state machine and interaction diagram.

The timing diagram uses the following time lines:

State time line

General value time line

A lifeline in a Timing diagram forms a rectangular space within the content area of a frame. It is

typically aligned horizontally to read from left to right. Multiple lifelines may be stacked within the sam

frame to model the interaction between them.

Summary:

UML2.0 is an enhanced version where the new features are added to make it more usable and efficient



12/10/14, 1:ML 2.0 - Overview

There are two major categories in UML2.0, One is UML super structure and another is UMLinfrastructure. Although the new diagrams are based on the old concepts but still they have additional

features.

UML 2.0 offers four interaction diagrams, the Sequence diagram, Communication diagram, Interaction

Overview diagram, and an optional Timing diagram. All four diagrams utilize the frame notation to

enclose an interaction. The use of frames supports the reuse of interactions as interaction occurrences


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